As is well known, only a small fraction of the energy developed in an internal combustion engine such as a piston engine, now in practically universal use in automotive applications, produces usable shaft horsepower. The major portion of the energy is dissipated to the atmosphere through the engine coolant system or the engine exhaust system.
In the past, many attempts have been made to reduce these losses or to convert the otherwise wasted energy to useful form, often by using the waste heat as a power source for a secondary power system. Examples of such prior proposals are disclosed in U.S. Pat. Nos. 3,228,189 and 3,479,817.
As far as is known, neither proposal nor other proposals of a similar nature have been used on a commercial scale. It is believed that the failure of the industry to adopt these proposals and similar proposals is due to their complexity, cost, lack of reliability, and the physical bulk of the equipment which renders their use, particularly in automotive applications, impractical.